Electric multicopters (multirotors or MR-VTOL vehicles) are helicopters that use multiple rotors, typically four or more, to lift off the ground. The frame is as simple as a cross with a motor at each corner. The use of four or more rotors allows complete control of the craft with simple fixed pitch propellers. Control is accomplished by varying the individual rotation speeds of the motors. The only moving parts on the craft are the motors/props. This means multicopters are mechanically very simple unlike traditional helicopters that require cyclic and collective control on the main rotor and collective control on the tail rotor. However, the traditional helicopter does have an advantage: although mechanically more complex, it can be controlled completely by a human pilot without electronic assistance.
It is not humanly possible to control a multicopter of the type being described without gyroscopically modulated motor control. Only “fly by wire” is possible and the wire must have some control capability.
Despite the mechanical simplicity of the multicopter, it has only recently become attractive to popular use in the hobby and UAV markets. This is in part because gyroscopic control requires high precision computers with accurate gyro and accelerometer input. Only in the last few years have these components become affordable and readily available. One can easily buy a 3-axis electronic gyro board and build a simple hobby radio controlled quadcopter. However, currently available commercial and home-built machines come at a safety risk. A simple, common mechanical failure can result in complete system loss and catastrophe for multicopter cargo.
The agility and hardware simplicity of these vehicles also makes them ideal candidates for high-risk missions and in both open and compact spaces. MR-VTOL vehicles have been used in the movie industry for filming, search and rescue missions, and food transport. Future applications of MR-VTOL vehicles are virtually unlimited, e.g., human transport, exploration, and autonomous robotic delivery. From these numerous examples of transport, one common theme emerges, the cargo is often valuable and can be irreplaceable. This feature makes it critical that redundant safety features be incorporated into these transport devices to in order to increase their viability in the marketplace.